Foil production

ABSTRACT

Vaporized material is condensed and solidified on the surface of a revolving drum from which the material is stripped as a foil. A leader or starter sheet is temporarily magnetically retained on the drum and extended to a takeup means to aid in starting continuous deposition and stripping. Electron beams are employed in various ways to vaporize the material.

United States Patent [72] Inventor 3,181,209 5/1965 Smith,.1r......................

John J. Conlon Westfield, NJ. Appl. No. 65,422

3,183,563 5/1965 Smith,.1r... 3,196,003 3,506,803

7/1965 Jenkin....... 4/1970 Hart FOREIGN PATENTS 736,310 9/1955 Great Britain...............

[22] Filed Aug.20,l970

[45] Patented Sept.28,1971

Assignee Phelps Dodge Corporation New York, N.Y.

0 ma mu M d m f m 1 3 F X R0 Primary Examiner- Attorney-Davis, H

[54] FOIL PRODUCTION 9 Claims, 7 Drawing Figs.

ABSTRACT: vaporized material is condensed and solidified on the surface of a revolving drum from whichthc material is stripped as a foil. A leader or starter sheet is temporarily magnetically retained on the drum and extended to a takeup means to aid in starting continuous de nd stripping. E1 ys to vaporize the position a ectron beams are employed in various wa 2,864,137 12/1958 Brennan....................... 164/64X material.

PATENIEDsErzamn 3,50 ,515

sum a or 2 F' v lnven/ar John J. Con/0n By Davisfloxiefaifhful/ 8 Hapgood Attorneys FOIL PRODUCTION This invention relates to a depositing of vaporized material onto a condensing surface so as to form foil. More particularly, the present invention relates to the continuous condensing of metal vapors onto a rotating drum and the continuous stripping of solidified foil from the drum. Further, this invention concerns the startup of vapor deposition foil manufacturing equipment and the means by which the vapor is generated.

It is diffieult to start a vapor-deposited foil process using a rotating drum for the condensing surface because it is necessary to pick off the drum the leading edge of the initial deposit while the drum is rotating. This picking off of the leading edge of the initial deposit may be accomplished with the drum stationary if the condensation is temporarily suspended. However, from the standpoint of speed and uniformity of foil quality, it is preferable to accomplish this picking off while the drum is rotating, With the drum stationary, the picking off of the initial foil may be accomplished at leisure over a period of hours or days and may involve numerous procedures including manual ones. On the other hand, with the drum turning, the pickoff must be accomplished during the time it takes the drum to make a partial revolution which, typically may be but a few seconds. Consequently, such a continuous start must be almost entirely automatic. Because of the several advantages of foil uniformity, speed, and the ability to initiate startup of a continuous foil-manufacturing process under vacuum conditions, a continuous startup procedure is to be preferred.

One aspect of the present invention is concerned with the initial startup of a continuous foil deposition process by employing a starter sheet leader temporarily retained on the condensing surface of the drum so that the initial deposit of condensed vapor is partly on the leader and partly on the condensing surface. The remainder of the leader is led to the foil takeup means such that the leader initiates pickoff of the deposited foil.

These and other features of the invention will be described with reference to the drawings in which:

FIG. 1 is a diagrammatic view of continuous vapordeposited foil apparatus in operation FIG. 2 is an enlarged cross-sectional view of a portion of the condensation drum showing the leader sheet in place, and

FIGS. 3a through 3d are diagrammatic views of the condensation drum, windup drum, and starter sheet showing the sequence of the startup operation.

Referring now to FIG. 1, a condensation surface in the form of a drum 1 is arranged to revolve about an axis 2. Material to be vaporized, for example copper, is provided in the form of a rod 33 which is progressively advanced downwardly and melted at the advancing end to form drops of molten copper 34. The melting of the supply rod 33 may be accomplished by various heat sources such as an electron beam source 31 which directs energy 32 toward the rod. The molten metal drops 34 are collected in a holding vessel 4 provided at its bottom with a drop-forming orifice 30 which permits drops to periodically fall from the holding vessel to wet 5 surface of a helical coil 5 in a manner described in U.S. Pat. No. 3,506,803. The helical coil is furnished with heat energy to cause the adherent film of molten metal to vaporize. The source of heat energy may be electrical resistance heating of the coil itself or may be, as shown, a source of energy such as a second electron beam source 6 which directs electron beam energy 7 to the wetted helical coil. Metal vapor 8 derived from the helical coil is condensed on the drum surface as a film 9 and solidifies to become the desired foil. In the illustrated apparatus more molten metal may be supplied to the top of the coil 5 than can be vaporized during its downward traverse of the coil. This excess molten metal drips from the lower extremity of the coil onto a sheet 37 which is curved to conform to the surface of the drum 1. Sheet 37 is made of a material which is wetted by the molten metal. Molybdenum or tungsten are wetted by molten copper. Thus, the molten metal which is drops from coil 5 appears as a thin film on the surface of sheet 37 proximate the drum. A source of heat energy such as a third electron beam source 35 is employed to direct energy 36 at the exterior surface of sheet 37 thereby heating the sheet to cause vaporization of the copper film on the interior surface of sheet 37.

Drum l is preferably cooled with a coolant to promote the condensation of vaporized material to form a film 9 which becomes the foil. A takeup roll 31 is arranged to strip the foil from the drum 1 and wind the foil into a convenient roll. The numeral 10 indicates the point at which the foil separates from drum 1.

The surface of drum 1 is of a material to which the condensed vapor adheres poorly. For example, when used for the production of copper foil, stainless steel is an appropriate surface material for the drum.

Turning now to FIG. 2, the drum 1 is shown in 116 section. Steel leader or startup sheet 12 is in the initial position conformed to the surface of the drum 1 and extends to the take up roll (not shown). The outer wall 13 of the drum and the inner wall 14 are spaced. The space between the inner and outer walls may be used for a coolant medium to promote condensation. A magnet 15 and magnetic circuit structure 16 serve to hold the steel starter strip 12 in position on the drum. In the case of copper foil manufacture, the leader 12 is a smoothed soft steel sheet about three-thousandths of an inch think and at least as wide as the foil width of the drum. It is held in position on the surface of the drum with one end parallel to the axis of the drum by the attractive force of magnet 15. Magnet 15 is one of a number of conventional U-shaped magnets in a line which extends across the width of the drum. Magnetic conductors 16 are small diameter soft I steel rods which traverse the space between the inner and outer walls 14 and 13 of the drum. Magnetic conductors 16 terminate near the surface of the outer wall 13 but are arranged so as to not penetrate that smooth surface. Constructors 16 provide magnetic attraction for leader 12 while offering less resistance to the flow of coolant between the walls 13 and 14 than would be offered by magnets if placed between the walls 13 and 14.

Bridge or filet 17 is of a material capable of being flowed simultaneously onto the end of leader l2 aNd onto the surface ofthe drum by brushing or the like, solidified in approximately the same shape and volume as the flowed liquid, and capable of adhering to the drum surface and to the leader, but with greater adherence to the leader so that the bridge 17 will remain adhered to the leader when it is pulled from the drum. The bridge material must be capable of withstanding relatively high temperature in the order of 400 F. in the case of copper foil without substantial gas evolution or other change in physical properties, and must be capable of forming a surface onto which the vapor will deposit and condense into foil with sufficient mechanical strength at the boundaries l8 and 19 so as to avoid fracture of the foil when the bridge 17 is parted from the drum as the leader 12 is wound onto the takeup roll 21. As an example of a material meeting these characteristics are vari ous silicone adhesive compounds such as that sold by Dow coming Corporation under the trade name ADHESIVE 28l. Such silicone adhesives display greater adhesion to the steel starter strip than to the stainless steel drum surface. Other materials can be used which meet the foregoing qualifications.

Turning now to FIGS. 3a though 3d the use of the starter strip 12 in starting up the continuous foil process is schematically illustrated in successive stages. FIG. 3a shows the leader 12 and drum 1 in the initial position before vapor deposition has commenced and before the drum has started rotating. FIG. 3b shows the situation a short while later after vapor deposition has commenced but before drum rotation has been started. FIG. 30 shows the situation at a time later than FIG. 3b after vapor deposition has commenced and after the drum has started rotating but before the leader 12 has become fully detached from the drum. FIG. 3d shows the situation after the leader 12 has fully detached itself from the drum.

Referring now to FIG. 3a, the leader 12 is shown with one end in the initial position on the drum. It is held there by magnets such as the magnetic structure is, 16 shown in FlG. 2. The other end of the leader 12 is wound about a take up roll 21 and attached by some temporary attaching means such as adhesive tape 22. The condition of FIG. 3ais that of no rotation of the drum or takeup roll and prior to the initiation of the vapor deposition.

Referring next to FIG. 3bwhich depicts the condition of no rotation of drum 1 or take up roll 21 but after initiation of the vapor deposition. The vapor is indicated generally as and the condensate of the vapor is indicated generally as 9. It can be seen that the condensed vapor 9 is formed partially on the exposed surface of the drum 1, over the bridge material 17, and extends onto the leader 12.

Referring now to FIG. 3c, the drum 1 has begun to rotate as has the takeup roll 21. The leader is now wound about the takeup drum. The leading edge of the initially deposited condensed vapor 9 is found on that portion of the leader which bridges the space between the condensation drum 1 and the takeup foil 21. The leader in FIG. 30 is shown just as it is about to leave the surface of the condensation drum 1 The bridge portion 17 is located at the point 10 where the foil and drum surfaces diverge. The deposited foil thickness is now sufficient, say five-thousandths of an inch, to provide a foil of suffcient mechanical strength'to endure being. stripped from the surface of the drum and wound about the takeup roll 21. It will be apparent that the magnetic and adhesive forces holding the leader 12 to the drum will be overcome by the tension exerted between the drum and the takeup roll 21 as the leader is wound about the takeup roll. The leader will accordingly be released from the drum carrying with it the initial portion of the continuous foil deposit.

Referring now to FIG. 3h, the situation illustrated is that after the leader has been pulled away from the condensation drum and wound about the takeup roll 21. The gap between the drum 1 and the roll 21 is now solely bridged by the deposited foil. Once the situation depicted by FIG. 3d has been reached, continuous deposition of the foil on the drum and accumulation of the foil on the roll can proceed.

it should be apparent that the use of such a leader technique for initiating a continuous foil deposition process permits a convenient and rapid means of initiating the stripping of the foil. Further, where the vapor is deposited under controlled atmospheric conditions such as a vacuum, the leader can be positioned on the drum and threaded through rolls or vacuum seals which may be employed and thence to the exterior of the deposition apparatus to a takeup drum.

While the invention has been described primarily with reference to copper foil manufacture, it is apparent that the invention has application with other materials which are capable of forming foils by vaporization and condensation on a drum surface. Such vapor condensation techniques are con ventional for various metals and can be employed for nonmetallic materials such as plastics.

Similarly, I have disclosed the use ofa steel leader, but it is apparent that other magnetic materials could be used. It is possible to use a nonmetallic sheet having incorporated into its composition metallic or ceramic magnetic powder. I have shown a plurality of discrete magnets 15 in the drum, but it is apparent that one long magnet could be used. Ceramic, metallic, or electromagnets can be employed. The magnetic conductors 16 can be strips of conductor material rather than the discrete bars shown.

What is claim is:

1. The method of starting up a continuous vapor deposition foil apparatus wherein vapor is continuously condensed as a film which solidifies as a low adherence foil on a movable surface, the foil being directed through tension exerting means to strip the foil from the movable surface, comprising the steps of:

placing a first end portion of a leader sheet of a magnetic material to which the condensed film will adhere on the movable surface, providing magnetic attraction between the leader and the movable surface to magnetically retain the leader thereon,

extending the other end portion of the leader at least to the tension-extending means,

condensing vapor on the movable surface and the said first end portion of the leader, and

exerting tension on the leader to overcome the magnetic retention of the leader to cause the leader to be stripped from the movable surface carrying with it the deposited foil.

2. The method of claim 1 including the steps of applying a coating ofa hardenable material to which the film will adhere and which is adherent to the leader over at least a portion of the movable surface and the first end portion of the leader, and hardening the coating.

3. In an apparatus for the continuous production of vapordeposited foil comprising a source of material to be vaporized, means to vaporize the material, a movable surface upon which the vapor is condensed as a film and solidified into a low adherence foil, and tension-exerting means to strip the foil from the movable surface, the improvement which comprises a leader sheet of magnetic material to which the film will adhere, a first end of the leader being positioned to overlie the movable surface in the region of vapor deposition, the remainder of the leader extending at least to the tension-exerting means such that the initially deposited vapor will form a continuous film on the leader and movable surface, and magnet means associated with the movable surface for magnetically retaining the first end of the leader in position on the movable surface.

4. The apparatus of claim 3 in which the movable surface is a drum and the magnetic means is a strip of magnetized material interior of the drum, extending axially of and proximate the surface of the drum.

5. The apparatus of claim 4 wherein the drum is hollow and a coolant is circulated through the interior.

6. The apparatus of claim 4 wherein the drum has radially spaced exterior and interior cylindrical walls and a coolant is circulated through the space.

7. The apparatus of claim 6 wherein the strip of magnetized material is interior of the interior cylindrical wall and mag netic conductor material extends radially through the space between the walls from the magnet poles to a point proximate the outer surface of the drum.

8. The apparatus of claim 7 wherein the strip of magnetized material is a plurality of individual magnets in a line and the magnetic conductor material is in the form of a plurality of radial rods, each having their interior end, proximate pole of a magnet.

9. The apparatus of claim 3 including a coating of hardenable material to which the film will adhere and which is adherent to the leader applied to and hardened on the said first end of the leader and at least the adjacent portion of the movable surface.

UNITED STATES PATENT OFFICE CERTIFICATE OF CURRECTION Patfint N0- 3,6O876L5 Dated Sgptember 28 v 197l Inv n John J Con] on It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 57, delete "5" and insert --the-- Col. 2; line 16, delete "116' and insert --partia1-- Col. 2, line 36, "Constructors" should be --Conductors-- Col 2, line hl, "aNd" should be --and-- Col. 2, line 57, "coming" should be "Corning-- Col. 3. line I, delete "is" and insert -l5-- Col. 3, line 9, between "as and" insert --8-' C01. 3, line 32, "311" should be --3d-- Col. 3 line 56, "nonmetallicl' should be --non-metal1ic-- Clairn 1 line 13, "extending should be --exe rting-- Signed and sealed this 9th day of May 1972.

Lisa AL EDAARU M.FLETCHER ,JR. ROBERT GOTTSCHALK Amos-ting Officer Commissioner of Patents 

2. The method of claim 1 including the steps of applying a coating of a hardenable material to which the film will adhere and which is adherent to the leader over at least a portion of the movable surface and the first end portion of the leader, and hardening the coating.
 3. In an apparatus for the continuous production of vapor-deposited foil comprising a source of material to be vaporized, means to vaporize the material, a movable surface upon which the vapor is condensed as a film and solidified into a low adherence foil, and tension-exerting means to strip the foil from the movable surface, the improvement which comprises a leader sheet of magnetic material to which the film will adhere, a first end of the leader being positioned to overlie the movable surface in the region of vapor deposition, the remainder of the leader extending at least to the tension-exerting means such that the initially deposited vapor will form a continuous film on the leader and movable surface, and magnet means associated with the movable surface for magnetically retaining the first end of the leader in position on the movable surface.
 4. The apparatus of claim 3 in which the movable surface is a drum and the magnetic means is a strip of magnetized material interior of the drum, extending axially of and proximate the surface of the drum.
 5. The apparatus of claim 4 wherein the drum is hollow and a coolant is circulated through the interior.
 6. The apparatus of claim 4 wherein the drum has radially spaced exterior and interior cylindrical walls and a coolant is circulated through the space.
 7. The apparatus of claim 6 wherein the strip of magnetized material is interior of the interior cylindrical wall and magnetic conductor material extends rAdially through the space between the walls from the magnet poles to a point proximate the outer surface of the drum.
 8. The apparatus of claim 7 wherein the strip of magnetized material is a plurality of individual magnets in a line and the magnetic conductor material is in the form of a plurality of radial rods, each having their interior end, proximate pole of a magnet.
 9. The apparatus of claim 3 including a coating of hardenable material to which the film will adhere and which is adherent to the leader applied to and hardened on the said first end of the leader and at least the adjacent portion of the movable surface. 